What is the next best treatment for a 57-year-old female with persistent constipation on MiraLAX (Polyethylene Glycol) daily with Dulcolax (Bisacodyl)?

Next Best Treatment for Persistent Constipation

For a 57-year-old female with persistent constipation despite MiraLAX (polyethylene glycol) daily with Dulcolax (bisacodyl), the next best treatment is to add lubiprostone 24 mcg twice daily with food and water. 1

Assessment of Current Regimen

The patient is currently on a combination of:

• MiraLAX (polyethylene glycol) - an osmotic laxative
• Dulcolax (bisacodyl) - a stimulant laxative

Despite this combination therapy, she continues to experience constipation, indicating treatment failure with first-line agents.

Treatment Algorithm

1. First-line therapy (current regimen):

   • Polyethylene glycol (osmotic laxative)
   • Bisacodyl (stimulant laxative)

2. Second-line therapy (recommended next step):

   • Add lubiprostone 24 mcg twice daily 2, 1

3. Alternative second-line options (if lubiprostone is not tolerated or available):

   • Linaclotide 72-145 μg daily 2
   • Plecanatide 3 mg daily 2
   • Prucalopride 1-2 mg daily 2

Rationale for Lubiprostone

Lubiprostone is specifically indicated for chronic idiopathic constipation in adults and works through a different mechanism than the patient's current regimen:

• Mechanism of action: Intestinal secretagogue that activates chloride channels in the intestinal lumen, increasing intestinal fluid secretion and motility 2, 1

• Efficacy: Clinical trials demonstrated that lubiprostone significantly increases spontaneous bowel movement (SBM) frequency compared to placebo, with effects seen within the first 24 hours (57-63% vs. 32-37%) 1

• Benefits beyond current therapy: Lubiprostone may also improve abdominal discomfort, bloating, and stool consistency 1, which are often persistent symptoms even when bowel movement frequency improves

• Complementary mechanism: Adding a secretagogue to the current osmotic and stimulant laxatives provides a multi-mechanism approach targeting different physiological pathways 2, 3

Administration Guidelines

• Take lubiprostone 24 mcg twice daily with food and water
• Swallow capsules whole; do not break apart or chew
• Taking with food reduces the risk of nausea, which is a common side effect 1
• Periodically reassess the need for continued therapy 1

Monitoring and Expectations

• Expect improvement in spontaneous bowel movements within 24-48 hours
• Monitor for side effects, particularly:
  • Nausea (most common)
  • Diarrhea
  • Abdominal pain
  • Headache
  • Potential for syncope and hypotension (rare) 1

Important Considerations

• Recent hyponatremia history: While the patient's hyponatremia has self-corrected, lubiprostone does not significantly affect electrolyte balance, making it a safer option than increasing osmotic laxative doses 1

• Avoid increasing PEG dose: Although higher doses of PEG (up to 68g) can provide more rapid relief 4, this approach may risk recurrence of electrolyte abnormalities in a patient with recent hyponatremia

• Avoid magnesium-based laxatives: Given the patient's recent history of electrolyte disturbance, magnesium-containing products should be avoided despite their listing in treatment guidelines 2

• Long-term safety: Lubiprostone has demonstrated safety and efficacy for long-term use in chronic constipation 1

If lubiprostone is not effective or not tolerated, consider a gastroenterology referral for further evaluation, including possible high-resolution manometry to better characterize the patient's constipation subtype and guide more targeted therapy 3.